/*
 * Hibernate, Relational Persistence for Idiomatic Java
 *
 * Copyright (c) 2009 by Red Hat Inc and/or its affiliates or by
 * third-party contributors as indicated by either @author tags or express
 * copyright attribution statements applied by the authors.  All
 * third-party contributions are distributed under license by Red Hat Inc.
 *
 * This copyrighted material is made available to anyone wishing to use, modify,
 * copy, or redistribute it subject to the terms and conditions of the GNU
 * Lesser General Public License, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
 * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public License
 * for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this distribution; if not, write to:
 * Free Software Foundation, Inc.
 * 51 Franklin Street, Fifth Floor
 * Boston, MA  02110-1301  USA
 */
package org.hibernate.engine.jdbc;

import java.io.Serializable;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.sql.Clob;

import org.hibernate.HibernateException;

/**
 * Manages aspects of proxying {@link Clob Clobs} to add serializability.
 *
 * @author Gavin King
 * @author Steve Ebersole
 * @author Gail Badner
 */
public class SerializableClobProxy implements InvocationHandler, Serializable {
	private static final Class[] PROXY_INTERFACES = new Class[] { Clob.class, WrappedClob.class, Serializable.class };

	private transient final Clob clob;

	/**
	 * Builds a serializable {@link java.sql.Clob} wrapper around the given {@link java.sql.Clob}.
	 *
	 * @param clob The {@link java.sql.Clob} to be wrapped.
	 * @see #generateProxy(java.sql.Clob)
	 */
	protected SerializableClobProxy(Clob clob) {
		this.clob = clob;
	}

	public Clob getWrappedClob() {
		if ( clob == null ) {
			throw new IllegalStateException( "Clobs may not be accessed after serialization" );
		}
		else {
			return clob;
		}
	}

	/**
	 * {@inheritDoc}
	 */
	public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
		if ( "getWrappedClob".equals( method.getName() ) ) {
			return getWrappedClob();
		}
		try {
			return method.invoke( getWrappedClob(), args );
		}
		catch ( AbstractMethodError e ) {
			throw new HibernateException( "The JDBC driver does not implement the method: " + method, e );
		}
		catch ( InvocationTargetException e ) {
			throw e.getTargetException();
		}
	}

	/**
	 * Generates a SerializableClobProxy proxy wrapping the provided Clob object.
	 *
	 * @param clob The Clob to wrap.
	 * @return The generated proxy.
	 */
	public static Clob generateProxy(Clob clob) {
		return ( Clob ) Proxy.newProxyInstance(
				getProxyClassLoader(),
				PROXY_INTERFACES,
				new SerializableClobProxy( clob )
		);
	}

	/**
	 * Determines the appropriate class loader to which the generated proxy
	 * should be scoped.
	 *
	 * @return The class loader appropriate for proxy construction.
	 */
	public static ClassLoader getProxyClassLoader() {
		ClassLoader cl = Thread.currentThread().getContextClassLoader();
		if ( cl == null ) {
			cl = WrappedClob.class.getClassLoader();
		}
		return cl;
	}
}
